Several prior techniques have been developed to process and deal with the MIMO communication system including:
(1) In MIMO systems, it is known that high spectral efficiency and high quality can be achieved by exploiting the spatial multiplexing (SM) scheme ‘[G. D. Golden, G. J. Foschini, R. A. Valenzuela, and P. W. Wolniansky, “Detection algorithm and initial laboratory results using V-BLAST space-time communication structure,” Electronic Letters, vol. 35, no. 1, pp. 14-161, January 1999] (hereafter referred to as REF. 1) and space-time coding (STC) [V. Tarokh, H. Jafarkhani, and A. R. Calderbank, “Space-time block codes from orthogonal designs,” IEEE Trans. Inform. Theory, vol. 45, no. 7, pp. 1456-1467, July 1999] (hereafter referred to as REF. 2) scheme, respectively. Such schemes can be directly applied to the multiuser (MU) systems yielding an MU SM system or an MU STC system. However, whenever in which the system, the data streams of all the users must be transmitted under the same mode and cannot be switched. This is very inflexible and cannot achieve the best performance for a general system link requirement and/or wide channel conditions.
(2) Naguib's 2-step Method [A. F. Naguib, N. Seshadri, and A. R. Calderbank, “Applications of space-time block codes and interference suppression for high capacity and high data rate wireless systems,” Proc. 32th Asilomar Conf. Signals, Systems, and Computers, vol. 2, pp. 1803-1810, 1998] (hereafter referred to as REF. 3) can be directly implemented an MU STBC system. In this scenario, the overall detection framework can be simply regarded as a parallel interference cancellation (PIC) scheme followed by a local ML search. In such a processing, the signal detection thus cannot enjoy the increased receive diversity gain through the PIC step. On the other hand, this method is based on the ML metric to decide the optimal detection order. This may achieve better detection performance but, however, attain a large computational cost.
(3) The method proposed in [V. Tarokh, A. Naguib, N. Seshadri, and A. R. Calderbank, “Combined array processing and space-time coding,” IEEE Trans. Inform. Theory, vol. 45, no. 4, pp. 1121-1128, May 1999] (hereafter referred to as REF. 4) applies the BLAST algorithm for signal detection followed by an ML search in single user (SU) systems. However, the algorithm is mainly based on the space-time trellis codes, and do not exploit the codeword's algebraic structures for decoding.
(4) in the Stamoulis's method [A. Stamoulis, N. Al-Dhahir, and A. R. Calderbank, “Further results on interference cancellation and space-time block codes,” Proc. 35th Asilomar Conf Signals, Systems, and Computers, vol. 1, pp. 257-261, 2001] (hereafter referred to as REF. 5) is a pure interference cancellation scheme through appropriate linear transformation based on the algebraic structure of orthogonal based space-time block coding (O-STBC) to decouple a user's data stream one at a time over the MU STBC systems. At each stage, there are no increased degrees-of-freedom that can be retained after the interference cancellation step for further interference suppression/signal detection at the next stage. This causes that it cannot enjoy the increase in receive diversity as the algorithm goes on, even if it is combined with some power ordering strategy.